Abstract: In this paper, the soil water characteristic curves for different depths from 0 cm to 150 cm of the soil in Tarim Desert highway shelterbelt were measured with Pressure Membrane Apparatus and were analyzed with van Genuchten Model and Gardner Model, of which the differences were compared. The results showed as follows:(1) The structural differences among the depths of the soil profile could be reflected by the measured soil water characteristic curves, resulting from the correspondence between the features of the curves and the soil basic physical properties at different depths of soil. Briefly, the characteristics that the capacity of soil water retention was stronger, the saturated moisture content and residual moisture content were higher, which were consistent with the features that the soil bulk was smaller and the proportion of the silts and clays were higher. Meanwhile, the capacities of soil water retention were similar as the differences of soil physical properties in various depths were slight.(2)Based on van Genuchten Model, the averages of soil saturated moisture capacity and wilting coefficient were 0.429 cm³·cm^-3 and 0.04 cm³·cm^-3. Based on Gardner Model, from strong to weak, the capacities of soil water retention for different depths were followed by 0-5 cm, 40-60 cm, 100-150 cm, 60-100 cm and 5-40 cm, respectively; overall, the suction on wilting coefficient was 15×10⁵ Pa and it took 1.5×10⁵ Pa as the boundary point of suction for the readily available water and the resistant available water.And all the above results were reasonable, which were according with the properties of the sandy soil.(3) The fitted precision of van Genuchten Model was higher in the low suction less than 1.0×10⁵ Pa while the fitted precision of Gardner Model was a little higher in the above suction from 1.0×10⁵ Pa to 15.0×10⁵ Pa. However, on the whole, the former was superior to the latter on fitting the soil water characteristic curves, because the results of correlation coefficients and root-mean-square errors between simulated values and measured values of soil moisture content with van Genuchten Model were better than the values calculated with Gardner Model. Summarily, both of the models can be used to fit the soil water characteristic curve of this region. It is aimed to reserve the characteristics of soil water curve and its optimal fitting model, making theoretical preparation for the study on dynamic simulation and prediction on soil water and salt in Tarim Desert highway shelterbelt.

Key words: soil water characteristic curve, Pressure Membrane Apparatus, van Genuchten model, Gardner model, Tarim Desert Highway shelterbelt